How can I make the list of letters from A to Z and iterate through them in the shell?

Question

Say I want to iterate from letter A to letter Z in csh shell. How do I succinctly do that?

In bash I would do something like

for i in 'A B C ...Z'; do echo $i; done

The point is I don't want to write A through Z, I want something like

[A-Z]

Can you suggest a one line suggestion in AWK or Perl?

Answer 1

foreach i (`jot -c 26 65`)
    echo $i
end

Answer 2

perl -e 'print for "a" .. "z", "A" .. "Z", 0 .. 9'

Answer 3

Perl

$,=" ";print +(A..Z)

or to use inside a shell:

for i in `perl -e '$,=" ";print +(A..Z)'` ; do echo $i ; done

Answer 4

How about:

for i in $(perl -e 'for my $i ("a".."z") { print "$i "; }'); do ...; done

... or am I misunderstanding what you're trying to accomplish?

(Admittedly the suggestion using $,=" " is even better than the explicit Perl for loop). However, I don't understand value of wrapping the range in +() punctuation. It works for me if I just use: print A..Z; ... though perl -we 'print a..z;' gives me a warning about unquoted strings, but the uppercase version doesn't. The statement print +(a..z) gives exactly the same warning ... and quoting any of these eliminates the warning. So what's the intent of the +(...)`? Is it just trying to force this into a list context?)

Answer 5

Hope you have Ruby installed. ;) See this, plain command-line from the shell:

1. using Ruby to iterate from A to Z and ask to print the letters:

   $ ruby -e ' "a".upto("z") {|letter| print letter}; print "\n"'
   

2. iterate from A to Z and substitute the value obtained during the current iteration into a string, then print the string:

   $ ruby -e ' "a".upto("z") {|letter| puts "mkdir #{letter}"}'
   

   mkdir a
   mkdir b
   mkdir c
   mkdir d
   ...
   mkdir z
   

3. use the output of the iteration from A to C as an argument to mkdir, in order to create 3 directories:

   $ mkdir $(ruby -e ' "a".upto("c") {|letter| puts "#{letter}"}')
   

   do a listing to see the results:

   $ ls -al
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 a
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 b
   drwxr-xr-x  2 iuliu users  4096 2009-10-07 00:09 c
   

Hope this helps a bit! ;)

regards, Iuliu

Answer 6

nobody has gawk solution, therefore here's one

awk 'BEGIN{for(i=65;i<=90;i++) printf "%c", i}'